Patent Grant
11015067
This application is the U.S. National Phase Application of PCT/JP2018/029467, filed Aug. 6, 2018, which claims priority from JP 2017-152292, filed Aug. 7, 2017, the contents of which applications are incorporated herein by reference in their entireties for all purposes.
The present invention is related to a slurry for flexible electrodes and a flexible electrode using the same.
In recent years, actuators using polymer materials such as carbon nanotubes, ion conductive polymers, and dielectric elastomers have been proposed. Among them, actuators using a polymer material such as a dielectric elastomer (hereinafter referred to as a dielectric actuator) or the like are expected to be used in various fields such as artificial muscles, medical devices, nursing aids, and industrial robots because of their large output.
As illustrated in
Here, when the flexibility of the electrode is poor, it is difficult to obtain a desired amount of displacement because the electrode may prevent the dielectric layer from being extended or contracted, or the electrode may break. Therefore, it is desirable that the electrode be flexible so as not to disturb the deformation of the dielectric layer and not to break. A flexible electrode can be produced, for example, by coating slurry made of a conductive agent on a slurry made of a base material such as rubber or elastomer. In this case, it is necessary to disperse the conductive agent throughout the base material in order to ensure the conductivity of the electrode. For this reason, the filling amount of the conductive agent is increased. When the filling amount of the conductive agent is increased, the conductivity at the natural length of the electrode is improved, but the electrode may break at the time of extending and the conductivity may be lost. Furthermore, the viscosity of the slurry increases, making coating difficult. On the other hand, if the filling amount of the conductive agent is reduced in order to ensure flexibility and coatability, the conductivity is lowered and electric charge cannot be supplied to the dielectric layer sufficiently. In addition, when the electrode is greatly extended together with the dielectric layer, the distance between the conductive agents is increased, so that the conductive path is cut and the electric resistance is increased. Thus, an electrode slurry, which satisfies a desired conductivity, flexibility, and coatability at the same time, has not yet been realized.
As an improvement measure, there is a method using a slurry in which carbon nanotubes are dispersed in a matrix. (Patent Document 1)
[Patent Document 1] JP4771971B1
However, since it is indispensable to use CNT which is a nanomaterial in patent document 1, it is necessary to take into consideration the possibility of an influence on health. In addition, the volume resistance value at the time of 150% elongation is 80 Ωcm or more. In addition, since organic solvent and ultrasonic homogenizer are used at the time of preparation of the electrode, there is a risk that the organic solvent may be heated and it may ignite.
The problem to be solved by the present invention is to provide a slurry such that the change in resistance value when the electrode is extended can be suppressed, and a flexible electrode that does not break when extended can be produced.
The present invention is characterized in that a specific emulsion contains the following specific component (a), or containing the following component (a) and component (b).
Component (a):carbon black having a DBP absorption amount under uncompressed conditions of 150 to 300 mL/100 g and a BET specific surface area of 35 to 140 m2/g.
Component (b): one or more carbons selected from the group consisting of the following α,β, γ, and δ
α: carbon nanotube having a fiber diameter of 1 to 20 nm
β: graphene having a diameter of 0.5 to 10 μm
γ: graphite having a diameter of 0.5 to 10 μm
δ: carbon black having a DBP absorption amount under uncompressed conditions of 350 to 500 mL/100 g and a specific surface area of 800 to 1300 m2/g
Note that the DBP absorption amount under uncompressed conditions of carbon black in the present invention is a value measured in accordance with JIS K6217-4.
The emulsion comprises one or more polymer components selected from the group consisting of chloroprene polymers, urethane polymers, fluorine polymers, urea polymers, acrylic polymers, and butadiene polymers, and when the pH of the emulsion is 6.5 to 8.0, the dispersibility of specific components in the slurry can be improved.
The most important feature of the present invention is that the electric resistance value can be suppressed from increasing when the electrode is extended. Specifically, in the slurry of the present invention, since the above-mentioned specific components are uniformly dispersed in the specific emulsion, a uniform conductive path can be formed throughout a produced electrode. A flexible electrode having an electric resistance of less than 80 Ω·cm at 150% strain and an electric resistance of less than 500 Ω·cm at 200% strain, which does not break at the time of extension, can be produced.
Next, embodiments of the present invention will be described in detail.
The present embodiment is a slurry for a flexible electrode obtained by dispersing the above-mentioned component (a) in an aqueous emulsion having a pH of 6.5 to 8.0.
In the present embodiment, as the polymer component(s) contained in the emulsion, it is desirable to use the following component(s).
Polymer component(s): the emulsion comprising at least one polymer selected from the group consisting of chloroprene polymers, urethane polymers, fluorine polymers, urea polymers, acrylic polymers, and butadiene polymers. Among these, urethane polymers and chloroprene polymers are particularly preferable in terms of flexibility, conductivity and dispersibility.
The pH of the emulsion used in the present embodiment is preferably 6.5 to 8.0. When the pH of the emulsion is less than 6.5, the dispersibility of the component (a) may be deteriorated. When the pH of the emulsion is higher than 8.0, the dispersibility of the component (a) may be deteriorated.
In the slurry for a flexible electrode according to the present embodiment, the total of the polymer component(s) and the component (a) is preferably 20 to 30% by mass. If the total of the polymer component(s) and the component (a) is less than 20% by mass, the amount of water to be dried thus increases, and a uniform electrode may not be produced. On the other hand, if it is more than 30% by mass, the viscosity of the slurry for a flexible electrode thus increases, and the coatability may deteriorates.
In the slurry for a flexible electrode according to the present embodiment, of the total of the polymer component(s) and the component (a), the proportion of the polymer component(s) is preferably 60 to 85% by mass, and the proportion of the component (a) is preferably 15 to 40% by mass. If the proportion of the component (a) is less than 15% by mass, conductivity becomes difficult to be exhibited. Conversely, if the proportion of the component (a) is more than 40% by mass, the produced electrode becomes hard and may break, or the dispersibility may deteriorate.
The component (a) is preferably carbon black having a DBP absorption amount under uncompressed conditions of 150 to 300 (mL/100 g) and a BET specific surface area of 35 to 140 (m2/g). That is, if the DBP absorption amount under uncompressed conditions and the BET specific surface area are too small, the conductivity-imparting effect at the time of producing a flexible electrode may decrease, and if the DBP absorption amount under uncompressed conditions and the BET specific surface area are too large, the slurry will not be uniform.
Note that the DBP absorption amount under uncompressed conditions of carbon black in the present embodiment is a value measured in accordance with JIS K6217-4.
Further, in another present embodiment, the component (a) and a following component (b) may be used in combination.
Component (b): one or more carbons selected from the group consisting of the following α,β, γ, and δ
α: carbon nanotube having a fiber diameter of 1 to 20 nm
β: graphene having a diameter of 0.5 to 10 μm
γ: graphite having a diameter of 0.5 to 10 μm
δ: carbon black having a DBP absorption amount of under uncompressed conditions 350 to 500 mL/100 g and a specific surface area of 800 to 1300 m2/g
In the present embodiment, as the polymer component(s) contained in the emulsion, it is desirable to use the following component(s).
Polymer component(s): the emulsion comprising at least one polymer selected from the group consisting of chloroprene polymers, urethane polymers, fluorine polymers, urea polymers, acrylic polymers, and butadiene polymers. Among these, urethane polymers and chloroprene polymers are particularly preferable in terms of flexibility, conductivity and dispersibility.
The pH of the emulsion used in the present embodiment is preferably 6.5 to 8.0. When the pH of the emulsion is less than 6.5, the dispersibility of the component (a) may be deteriorated. When the pH of the emulsion is higher than 8.0, the dispersibility of the component (b) may be deteriorated.
In the slurry for a flexible electrode according to the present embodiment, it is preferable that the total of the polymer component(s) and the component (a) is 20 to 30% by mass. If the total of the polymer component, component (a), and component (b) is less than 20% by mass, the amount of water to be dried thus increases, and a uniform electrode may not be produced. On the other hand, if it is more than 30% by mass, the viscosity of the slurry for a flexible electrode thus increases, and the coatability may deteriorates.
In the slurry for a flexible electrode according to the present embodiment, of the total of the polymer component(s), the component (a) and the component (b), it is preferable that the polymer component(s) is 60 to 85% by mass, and the total of the component (a) and the component (b) is 15 to 40% by mass. When the total of the component (a) and the component (b) is less than 15% by mass, conductivity becomes difficult to be exhibited, and when the total of the component (a) and the component (b) is more than 40% by mass, the produced electrode becomes hard and may break, or the dispersibility may deteriorate.
In the slurry for a flexible electrode according to the present embodiment, it is preferable that of the component (a) and the component (b), the component (a) is 50 to 90% by mass, and the component (b) is 10 to 50% by mass. If the component (b) is less than 10% by mass, the effect of improving the conductivity of the flexible electrode cannot be obtained. If it is more than 50% by mass, the produced electrode becomes hard and may breaks during extending.
The carbon nanotube in the component (b) preferably has a fiber diameter of 1 to 20 nm. That is, if the fiber diameter is too small, the dispersibility tends to deteriorate, and the physical properties tend to decrease. Conversely, if the fiber diameter is too large, the conductivity tends to decrease during the production of the flexible electrode.
The graphene in the component (b) preferably has a diameter of 0.5 to 10 μm. That is, if the diameter is too small, the conductivity decreases during the production of the flexible electrode. Conversely if the diameter is too large, the flexible electrode tends to break during elongation.
The graphite in the component (b) preferably has a diameter of 0.5 to 10 μm. That is, if the diameter is too small, the conductivity decreases during the production of the flexible electrode, and if the diameter is too large, the flexible electrode tends to break during elongation.
The carbon black in the component (b) preferably has a DBP absorption amount under uncompressed conditions of 350 to 500 (mL/100 g) and a BET specific surface area of 800 to 1300 (m2/g). That is, if the DBP absorption amount under uncompressed conditions and the BET specific surface area are too small, the conductivity-imparting effect at the time of producing a flexible electrode may decrease, and if the DBP absorption amount under uncompressed conditions and the BET specific surface area are too large, the slurry will not be uniform.
Note that the DBP absorption amount under uncompressed conditions of carbon black in the present invention is a value measured in accordance with JIS K6217-4. Further, the carbon black is preferably acetylene black.
Further, in the flexible electrode of the present invention, in addition to the above components, for example, ionic conductive agents (surfactants, ionic liquids, ammonium salts, inorganic salts), metal particles, conductive polymers, plasticizers, oils, crosslinking agents, anti-aging agents, flame retardants, coloring agents and the like may be appropriately used.
The slurry for a flexible electrode of the present invention can be produced, for example, as follows. That is, the emulsion, the component (a) and the component (b) are blended and dispersed by using a dispersing device such as a rotation/revolution type mixer, a media mill, a three-roller, a stirrer, and a supersonic device to prepare a slurry. Then, the slurry is coated on a chloroprene sheet so as to have a predetermined thickness (preferably 1 to 100 μm), and dried and/or cross-linked under a predetermined condition (for example, at 100° C. for 30 minutes), so that a flexible electrode can be made.
The slurry for a flexible electrode of the present invention preferably has the following characteristics.
(1) A shear viscosity at a shear rate of 1.0 s−1 is 0.7 Pa·s to 50 Pa·s.
(2) A median diameter D50 of particles in the slurry is 0.1 to 10 μm.
The flexible electrode using the slurry of the present invention can be used, for example, for electronic devices such as actuators, sensors, and transducers. Therefore, another aspect of the present invention is a flexible electrode using the slurry of the present invention, and yet another aspect is an actuator, sensor, or transducer using the flexible electrode of the present invention. The purpose of producing an electrode having both conductivity and flexibility can be achieved without using a powerful dispersion device.
Next, examples and comparative examples will be described. However, the present invention is not limited to these examples.
First, prior to Examples and Comparative Examples, the following materials were prepared.
[Urethane Emulsion 1]
Superflex 300 manufactured by DKS Co. Ltd. (pH: 7.4, solid content: 30.2 (% by mass))
[Chloroprene Emulsion 1]
LC-21 manufactured by Denka Company Limited (pH: 7.0, solid content 30.2 (% by mass))
[Chloroprene Emulsion 2]
LV-60A manufactured by Denka Company Limited (pH: 12.0, solid content: 60.0 (% by mass))
[Carbon Black A (Component (a)]
DENKA BLACK FX-35 manufactured by Denka Company Limited (DBP oil absorption amount under uncompressed conditions: 267 (mL/100 g), BET specific surface area: 133 (m2/g))
[Carbon Black B (Component (a)]
DENKA BLACK HS-100 manufactured by Denka Company Limited (DBP oil absorption amount under uncompressed conditions: 177 (mL/100 g), BET specific surface area: 39 (m2/g))
[Carbon Black C (Component (a)]
DENKA BLACK AB powder manufactured by Denka Company Limited (DBP oil absorption amount under uncompressed conditions: 228 (mL/100 g), BET specific surface area: 68 (m2/g))
[Carbon Black D (Component (a)]
SuperP manufactured by Imerys Graphite & Carbon (DBP oil absorption amount under uncompressed conditions: 233 (mL/100 g), BET specific surface area: 62 (m2/g))
[Carbon black E (component (b)]
KETJENBLACK ECP300 manufactured by Lion Specialty Chemicals Co., Ltd. (DBP oil absorption amount under uncompressed conditions: 365 (mL/100 g), BET specific surface area: 800 (m2/g))
[Carbon Black F (Component (b)]
KETJENBLACK ECP600JD manufactured by Lion Specialty Chemicals Co., Ltd. (DBP oil absorption amount under uncompressed conditions: 495 (mL/100 g), BET specific surface area: 1270 (m2/g))
[Carbon Nanotube (Component (b)]
Flotube 9000 manufactured by Jiangsu Cnano Technology Limited (fiber diameter: 10 (nm)).
[Graphene (Component (b)]
Graphene powder manufactured by Aldrich (Diameter 5 (μm)).
[Graphite (Component (b)]
Graphite J-SP manufactured by Nippon Graphite Industries, Co., Ltd. (Diameter 7 (μm))
Next, a flexible electrode was produced using each of the above materials as described below.
60.0 parts by mass of chloroprene emulsion 1 was weighed out and mixed with 40.0 parts by mass of carbon black B. 0.05 parts by mass of a dispersant for carbon black was added with respect to carbon black B. After adding water so that the mass % of the polymer component+component (a) in the slurry becomes 20 mass %, the mixture is dispersed using a rotation/revolution mixer (Awatori Rentaro ARV-310 manufactured by THINKY CORPORATION) and thus a slurry for flexible electrode was prepared. Then, on a chloroprene sheet having a thickness of 0.3 mm, the slurry for flexible electrode was coated so as to have a thickness of 30 μm, and dried at 100° C. for 30 minutes to produce a flexible electrode.
A slurry for a flexible electrode was prepared in the same manner as in Example 1 except that the types and mixing ratios of each component were changed as shown in Tables 1 to 8. Then, flexible electrodes were prepared in the same manner as in Example 1 using these flexible electrode slurries.
Using the flexible electrode slurry and the flexible electrode thus obtained, each characteristic was evaluated in accordance with the following criteria. These results are also shown in Tables 1 to 8 above.
[Slurry Viscosity]
The viscosity of each slurry for flexible electrode was measured using a cone-plate viscometer (MCR-300, manufactured by Anton Paar GmbH). The measurement conditions were as follows:
Measurement mode: shear mode
Shear rate: changed from 100 s−1 to 0.01 s−1
Measurement jig: cone plate (CP-50-2; diameter 50 mm, angle 2°, gap 0.045 mm)
Measurement temperature: 25° C.
[Agglomeration Diameter in Slurry (Median Diameter D50)]
[Preparing Measuring Sample]
0.5 g of the slurry for flexible electrode was weighed into a vial, and 25.0 g of distilled water was added. A bath-type ultrasonic cleaner was used for pre-measurement treatment, and the sample was homogenized by ultrasonic irradiation to prepare a measurement sample.
[Measurement of Median Diameter D50]
Using the measurement sample prepared by the above method, the median diameter D50 value of the aggregation diameter in the slurry for flexible electrode was measured according to the following method. The optical model of the LS 13 320 universal liquid module is set to carbon, 1.520 and water 1.333 as the refractive indexes repectively, and the module is washed. After performing offset measurement, optical axis adjustment, and background measurement under the condition of a pump speed of 50%, the prepared measurement sample was add to a particle size analyzer so that the relative density indicating the percentage of light that the particles scatter to the outside of the beam by the particles is 8 to 12% or so that the PIDS is 40 to 55%, and then ultrasonic irradiation was performed at 78 W for 2 minutes using a device attached to the particle size particle size analyzer (measurement pretreatment), and the particles were circulated for 30 seconds to remove air bubbles, and then the particle size distribution was measured. A graph of the volume % with respect to the granularity (particle size) was obtained, and the median diameter D50 value was obtained.
The measurement was carried out by changing the sampling location for each sample of the slurry for flexible electrode to obtain three measurement samples, measuring the particle size distribution, and determining the median diameter D50 value using the average value.
[Volume Resistance Value]
The volume resistance at 0% strain, the volume resistance at 100% strain, the volume resistance at 150% strain, and the volume resistance at 200% strain of each flexible electrode were evaluated as follows. The flexible electrode is cut into a strip having a length of 2 cm and a width of 6.5 cm, and both ends are fixed with a tensile jig as shown in
For the slurries and electrodes produced in the Examples and Comparative Examples, the state of slurry mixing and the smoothness of the electrodes were visually evaluated. From the results shown in Tables 1 to 8, the Examples showed that the slurry mixing state was uniform and the electrodes had good smoothness as compared with the Comparative Examples. The Examples was excellent in conductivity and also excellent in conductivity after extension. This is because in these Examples, the carbon material is sufficiently uniformly dispersed in the electrode, and the conductive path is formed evenly during the extension.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2017-152292 | Aug 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/029467 | 8/6/2018 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/031460 | 2/14/2019 | WO | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20200165469 A1 | May 2020 | US |
